Highly-drafted,sinusoidal patterned nonwoven fabric laminates and method of making same

ABSTRACT

A NONWOVEN FABRIC COMPRISING AT LEAST ONE LAYER OF HIGHLY-DRAFTED, STAPLE LENGTH FIBERS EXTENDED TO SUBSTANTIALLY THEIR FULL LENGTH AND ARRANGED IN A SINUSOIDAL PATTERN WITH THE FIBERS EMBEDDED IN AND BONDED BY A SPACED PATTERNED LAYER OF FLEXIBLE ADHESIVE TO AT LEAST ONE LAYER OF LIGHTWEIGHT CELLULOSE WADDING AND THE METHOD OF MAKING SAME ARE DISCLOSED. ALSO DISCLOSED IS THE METHOD AND PRODUCT RESULTING FROM LAMINATING TWO SUCH NONWOVEN FABRICS TOGETHER WITH THE FILTER LAYERS FACING ONE ANOTHER AND WITH THE SINUSODIAL PATTERN OF FIBERS IN THE OPPOSING LAYERS OUT OF PHASE WITH ONE ANOTHER.   D R A W I N G

Jan. 5, 1971 R. H. WIDEMAN HIGHLY-DRAFTED SINUSOIDAL PATTERNED NONWOVENFABRIC LAMINATES AND METHOD OF MAKING SAME 2 Sheets-Sheet 1 Filed May20, 1966 Jam. 5, 1971 w M 3,553,064

HIGHLY-DRAFTED I U DAL P TERNED NONWOVEN FABRIC LAMI ES AND M OD OFMAKING SAME Filed May 20, 1966 I 2 Sheets-Sheet 2 United States Patent3,553,064 HIGHLY-DRAFTED, SINUSOIDAL PATTERNED NONWOVEN FABRIC LAMINATESAND METH- OD OF' MAKING SAME Ronald H. Wideman, Menasha, Wis., assignorto Kimberly-Clark Corporation, Neenah, Wis., a corporation of DelawareFiled May 20, 1966, Ser. No. 551,605 Int. Cl. B32b /12, 7/14; D04h 1/74U.S. Cl. 161-59 Claims ABSTRACT OF THE DISCLOSURE A nonwoven fabriccomprising at least one layer of highly-drafted, staple length fibersextended to substantially their full length and arranged in a sinusoidalpattern with the fibers embedded in and bonded by a spaced patternedlayer of flexible adhesive to at least one layer of lightweightcellulose wadding and the method of making same are disclosed. Alsodisclosed is the method and product resulting from laminating two suchnonwoven fabrics together wtih the fiber layers facing one another andwith the sinusoidal pattern of fibers in the opposing layers out ofphase with one another.

This invention relates to an improved process for the manufacture ofnonwoven webs and to products obtained thereby. More specifically itrelates to a process for forming a bonded nonwoven web from a laminationof highly-drafted fibers and a carrier sheet.

It is known that individual textile fibers may be drawn out andsubstantially aligned to form a thin web-like layer by passing an arrayof juxtaposed slivers of staple length fibers through a multiple rolldraw frame. The layer of fibers discharged from such a device is flimsy,film-like and gossamer in character, and, to be useful in web form whilestill retaining its highly-drafted alignment, must be immediately bondedto each other by some means, or supported by and bonded to assupplementary web. Highly-drafted fiber Webs have approximately 80% to95% of the fibers oriented substantially in the longitudinal direction.As disclosed in U.S. Pat. No. 3,327,708, such a high degree of fiberalignment is desirable in that it contributes substantially to improvedlongitudinal strength properties per unit weight when compared withprior art carded fiber webs in which only about 50% to 70% of the fibersare longitudinally aligned. However, while this high degree of fiberalignment improves the longitudinal strength, the transverse strength ofthe resulting web is lessened because of the relative paucity ofcrossing fibers, even though the bonding means may comprise transverselines of strong adhesive or the like. Ordinarily this problem may beovercome by cross-laying and bonding two such webs together whereby thestrength in each direction is equalized as disclosed in copendingSaunders et a1. application Ser. No. 498,929, filed Oct. 20, 1965 andassigned to the same assignee as the present application. However, knowncross-laying methods usually entail either costly or low-speedequipment, adding considerable expense to the cost of the finishedproduct.

The present invention overcomes the latter difiiculties and provides adrawn-fiber nonwoven web of high trans verse strength 'withoutcross-laying.

Accordingly, a primary object of the invention is to provide a processfor fabricating a nonwoven web having "ice improved cross-directionstrength from a laminate of highly-drafted fibers and an integralcarrier sheet.

Another object is to provide a laminated web in which at least oneelement is an array of highly-drafted and aligned fibers, and a secondelement comprises a carrier sheet to which the highly-drafted andaligned fibers are bonded in a regular sinusoidal pattern.

An additional object is to provide a laminated web comprised of multiplelayers of highly-drafted substantially parallelized fibers arranged in aregular sinusoidal pattern combined with tissue carrier sheets.

Still another object is to provide a method for the economical,high-speed manufacture of 'webs of the character indicated.

Other objects and advantages will become apparent to persons skilled inthe art upon examination of the following description and drawings.

In the drawings:

FIG. 1 is a diagrammatic view in persepective of a device suitable forcarrying out one embodiment of the process of this invention.

FIG. 2 illustrates in side elevation a schematic arrangement for foldingand further laminating the web produced by the device of FIG. 1.

FIG. 3 is a front elevation of the arrangement shown in FIG. 2.

FIG. 4 is a representation of the appearance of a laminated productfabricated as taught herein, when viewed by transmitted light.

In one embodiment of the invention, as shown in FIG. 1, multiple sliversof textile fibers 11 are drawn from their respective supply cans over aguide comb 13 in juxtaposed relationship into a draw frame 15 comprisinga series of paired grooved rolls 14 and 14a. The rolls of each pair aredriven by appropriate gearing, well known in the art, at a peripheralspeed slightly faster than the rate of operation of the preceding pairto draw out and align the individual fibers from the slivers intosubstantially parallelized arrangement with the fibers extended to theirfull length. The drawn fibers are discharged from draw frame 15 in theform of a flat web 16 in substantially aligned arrangement. Web 16 is ofsuch flimsy and gossamer-like character that it must be quicklydeposited on a supporting carrier sheet 17 immediately after dischargefrom draw frame 15 in order to maintain its form. While other types ofcarrier sheets may be employed for this purpose, in the particularembodiment here shown and described, the carrier sheet 17 comprises asingle ply of lightweight cellulose wadding which eventually becomes anintegral part of the finished product. Wadding sheet 17 preferably hasbeen stretched and ironed to facial tissue softness by known means toprovide a like softness and hand to the finished product. However, forcertain products stretching and ironing may not be desirable.

The wadding sheet 17 is drawn from supply roll 21 into a nip formed by aprinting roll 22 and a back-up roll 24 maintained in very light pressureengagement with sheet 17. In this case, the surface of printing roll 22is provided with an intaglio pattern 23 which picks up adhesive 25 fromdip pan 26. Excess adhesive is scraped off by doctor blade 27. Theadhesive preferably is a low viscosity thermoplastic adhesive whichremains substantially on the surface of the wadding in the form of thepattern selected.

The pattern shown on the drawing comprises parallel, discontinuoustransverse lines in a brick-like design as shown at 18 merely forillustrative purposes, it being understood that the adhesive actually ison the underside of sheet 17 at this point. The printed sheet 17,bearing adhesive 18 on its undersurface, is then drawn around roll 19positioned adjacent the discharge end of draw frame 15 at which pointthe adhesive is on the upper surface and the drawn fiber web 16 isdeposited thereon. Roll 19, in addition to rotating in the directionshown, is also simultaneously oscillated transversely as indicated bydouble arrow 12, by known means, such as by a mechanized Scotch yoke orsimilar device. Because wadding sheet 17 is flexible, the oscillatingroll 19 can move the sheet back and forth transversely without tearingthe sheet. The drawn fiber web 16 is discharged from the draw frame withthe fibers aligned substantially in the direction of discharge. However,when the aligned fibers are deposited on the adhesive printed sheet 17a,the oscillating motion causes the web to take the form of a sinusoidalpattern shown at while the fibers still remain substantially parallel toone another. The adhesive 18 has suflicient tack and viscosity to holdthe fibers in alignment in spite of the oscillating movement. As aresult, the sinusoidal pattern comprises individual fibers in asubstantially parallel wave-like arrangement. While the sinusoidalpattern 10 is shown as parallel continuous lines, this showing is merelyfigurative. In reality, the web at this stage comprises a multiplicityof individual fibers aligned in side-by-side arrangement in the patternillustrated by these continuous lines.

The combined sheet 17 and patterned fiber lay 10 is carried around guideroll 28 into prolonged contact with heated drum 20. The heat fuses andcures the adhesive to a substantially nontacky condition while thefibers are in firm contact with the drum surface. To provide this curingeffect, travel around a substantial portion of drum 20 as in the mannershown is desirable. The laminated web with the fibers partially embeddedin the adhesive then passes under a pressure roll, or calender roll .30,which presses the fiber layer more firmly into the adhesive to assurepermanent attachment. The laminated web is subsequently wound up in aroll 29.

The laminated product in roll 29 which comprises a drawn fiber web withthe fibers arranged in an aligned sinusoidal pattern and adhesivelybonded and laminated to a lightweight cellulose wadding sheet, has alimited number of uses without further processing, especially for useswhere cross-direction strength is unimportant. However, a larger numberof potential uses are obtained when the resulting sheet is furtherlaminated to develop crossdirection strength.

One means of accomplishing this is shown in FIGS. 2 and 3. As shown inthese figures, the laminated sinusoidal pattern material produced in theabove-described manner is fed from supply roll 29a around guide roll 31,over a conventional V-shaped folding board or frame 32, between the nipof heated calender rolls 33, bringing the fiber side of the materialtogether in face-to-face contact to form laminated web 34 which is woundup into finished roll 35. The heat and pressure from the calender rollsactivates the adhesive causing portions, causing adhesive in one layerto intrude between the fibers in that layer to join the adhesive fromthe opposing layer whereby the laminated material is bonded togetherinto a unitary web. Selvage edge 36 subsequently may be trimmed ofl.

While the preferred embodiment of the folded laminated material has thefiber surfaces disposed face-to-face, the material may also have thewadding surfaces face-toface before calendering. However, the resultingproduct has less transverse strength than the preferred embodiment,probably because less adhesive migrates between layers to form bondsbetween sheets.

The appearance of the finished web 34, when viewed by transmitted light,is shown in FIG. 4. The arrangement as illustrated might be defined asthe overlapping of several parallelly-aligned vibrating strings in whichthe nodes 3-7 intersect and are bonded to each other, and the segments38 and 39 overlie and cross each other at multiple points to formadditional bonds. These multiple bonds form a diamond-like arrangementof fibers and adhesive and when force is exerted in a transversedirection provide flexible restraint and resilient cross-directionstrength.

While the above-described process provides bonding between thesinusoidal array of drawn fibers and the underlying carrier sheet bymeans of a thermoplastic adhesive previously applied to the carriersheet, another means of bonding may be used without materiallydisturbing the fiber alignment. In the latter case, a number of theslivers introduced into the draw frame may comprise thermoplasticfibers, or preferably, thermoplastic fibers may be mixed into eachsliver. A large variety of such man-made fibers are now availableincluding polyethylene, polypropylene, polyesters, polyacrylonitrile,polyvinyls, etc.

In one specific example, slivers were prepared containing 20%polypropylene fibers and rayon fibers. These mixed slivers were runthrough the draw frame as shown in FIG. 1 and described above. Roll 19was oscillated as before causing the highly-drafted fiber web emergingfrom the draw frame to be deposited on the carrier sheet in a uniformsinusoidal pattern of parallellyaligned fibers. No adhesive was appliedto the tissue carrier sheet. The fibers, nevertheless, retain thealigned sinusoidal pattern. It is not known why the fibers remainaligned in the wave pattern shown, but apparently, suflicientelectrostatic or frictional attraction exists between the carrier sheetand the drawn web to keep the pattern undisturbed. Upon hot calendering,a self-sustaining laminate was obtained. This product was in turn foldedand further laminated to provide a nonwoven web with improvedcross-directional strength, and having an appearance similar to thatshown in FIG. 4. The bonding strength in this instance coming from thethermoplastic nature of some of the fibers.

While a folding arrangement is shown in FIGS. 2 and 3 as the meansemployed to obtain the laminated product of FIG. 4, it will readily beseen that a similar product may be obtained by taking two rolls of theproduct obtained from the first stage of the process, and by running thewebs together in face-to-face arrangement between rolls of a heatedcalender stack for bonding purposes. To be effective with respect tocross-direction strength, however, the sinusoidal patterns of the websbefore lamination should be arranged with respect to one another so thatthe sinusoidal pattern in one web is out of phase from the sinusoidalpattern in the other web, to overlap and intersect the aligned fibers ofthe other web in the manner shown in FIG. 4.

While various well-known adhesives may be employed in the process,advantages reside in the use of plastisols, which, as is well known,comprise colloidal dispersions of synthetic resins in a suitable organicester plasticizer, and which, under the influence of heat, provide goodbinding power while remaining soft and flexible. While many adhesives ofthis type are known, those found particularly useful for incorporationin the product of this invention include vinyl chloride polymers, andcopolymers of vinyl chloride with other vinyl resins, plasticized byorganic phthalates, sebacates, adipates, or phosphates. These provide afast curing plastisol adhesive characterized by relatively lowviscosity, low migration tendencies, and minimum volatility. Suchadhesives remain soft and flexible after curing, can be reactivated bythe application of heat and pressure, such as by hot-calendering for theaforesaid lamination purposes, and insure that the resultant productretains a desirable softness and proper hand and feel.

While plastisols are preferred, polyvinyl resins per se, plasticized orunplasticized may also be used. Other flexible adhesives, which may beemployed, although generally less desirable, include materials such asacrylic resins like the alkyl acrylates and butadiene resins such asbuna-S and buna-N.

The adhesive pattern shown in the illustrations comprises a spacedbrick-like arrangement. Other well-known patterns may be employed, suchas spaced continuous parallel lines, spaced circles, dots, Vs,herringbones, etc. It is preferred that the pattern be substantiallyopen with large adhesive free areas. If flexibility is desired, it ispreferred that the total area occupied by the adhesive com prise notmore than 25% of the total area of the original fiber-wadding laminate.No matter what adhesive arrangement is chosen, care should be taken toassure that the adhesive-free area between adjoining adhesive patternsbe less in the longitudinal direction of the fibers than the averagelength of the individual fibers, in order that the integrity of the webis maintained.

The fibers .used in the process may comprise most of the staple lengthfibers employed in textiles. These include both natural and syntheticfibers such as cotton, viscose or acetate rayon, nylon, polyesters,acrylonitriles, polyolefins, and the like. When synthetic fibers areused, a denier range of 0.5 to 3 is preferred. However, coarser deniermay be used. It is also preferred that the fibers be of staple length,or in the range of /2 to about 3 inches or longer, with the majority offibers being at least one inch in length. For most purposes, the draftedWeb should be as light weight as possible commensurate withhandleability on the drawing frame. Suitable webs in the weight range of3 to 20 grams per square yard have been successfully drafted and bondedat speeds of from 20 feet per minute to well over 500 feet per minute.Webs of a higher weight may also be successfully made by this process.

While in the illustrated process, sheet 17 is oscillated transversely bymeans of oscillating roll 19, it will readily be seen that a sinusoidalpattern may also be obtained by oscillating the entire draw frame 15.

It will be apparent to those skilled in the art that many variationsfrom the examples given may be employed without departing from thespirit of this invention. For example, the weight of the startingslivers may be varied to provide adrawn web of varying thicknessthroughout its width. Similarly, various mixtures of thermoplastic andnonthermoplastic fibers may be used.

What is claimed is:

1. A method for producing a laminated web from layers of highly-draftedfibers and plies of cellulose Wadding; said method com-prising the stepsof providing multiple slivers of staple length textile fibers;juxtaposing said slivers in side-by-side relation and drawing theindividual fibers in said slivers out to substantially their full lengthwhile parallelly disposed with other drawn fibers to form a tenuous webof highly-drafted and longitudinally aligned individual fibers; applyinga thin layer of adhesive to a lightweight cellulose wadding sheet in aspaced pattern; positioning a continuous length of said adhesivecarryrng wadding under said aligned fiber tenuous web; moving saidtenuous web and said sheet in the same direction at approximately thesame speed and depositing said tenuous web on said adhesive printedwadding sheet while providing oppositely reciprocating side-to-sidemotion between said tenuous web and said wadding sheet at the pointwhere said tenuous web is deposited on said sheet in contact with saidadhesive whereby said tenuous web assumes a regular sinusoidal patternon said sheet; maintaining said fibers and said adhesive in contact,while applying heat thereto, and pressing said fibers firmly in saidadhesive to embed said fibers therein in said sinusoidal pattern, andcuring said adhesive.

2. The method of claim 1 in which fiber-faced surfaces of the resultingfiber-wadding sheet laminate are placed in face-to-face contact with thesinusoidal pattern of fibers in one of said surfaces out of phase withthe sinusoidal pattern of fibers in the opposing surface, and hotcalendering said contacting sheets to reactivate said adhesive,

causing said adhesive to migrate between fibers and bind said laminatesto each other.

3. The method of claim 2 in which the fiber-faced surfaces are placed inface-to-face contact by folding.

4. The method of claim 2 in Which the fiber-faced surfaces are placed incontact by aligning separately formed sheets of said laminate.

5. An adhesively bonded nonwoven fabric consisting essentially of atleast one layer of highly-drafted individual staple length fibersextended to substantially their full length and arranged in a sinusoidalpattern wherein the individual fibers are substantially parallel to eachother, at least one layer of lightweight cellulose wadding, and a layerof flexible adhesive between said fiber layer and said wadding layer tobond said layers together; said adhesive being arranged in a spacedpattern and partially penetrating said wadding; said fiber layer beingembedded and held in said adhesive.

6. An ahesively-bonded nonwoven fabric consisting essentially of outerlayers of lightweight cellulose wadding, inner layers of highly-draftedindividual staple length fibers extended to substantially their fulllength and arranged in a sinusoidal pattern wherein the individualfibers are substantially parallel to each other, and a layer of flexibleadhesive in a predetermined pattern between each of said wadding layersand said fiber layers; said fiber layers being arranged in face-to-facerelationship so that the sinusoidal pattern of one layer is out of phasewith the sinusoidal pattern of the opposing layer and the fibers in onelayer cross the fibers in the adjoining layer; said adhesive partiallypenetrating said wadding layers with the fibers embedded in saidadhesive and with portions of said adhesive between one fiber layer andone wadding layer extending between fibers in one layer to join portionsof said adhesive extending between the fibers of the other fiber layerand bonding the layers into a unitary fabric.

7. The fabric of claim 6 in which the adhesive is a plastisol.

8. The fabric of claim 6 in which the fibers are selected from the groupconsisting of cotton, viscose, acetate, rayon, nylon, polyesters,acrylonitriles, and polyolefins.

9. The fabric of claim 8 in which the fibers are in the denier range of0.5 to 3.

10. The fabric of claim 8 in which the fibers have a length in the rangeof about /2 to about 3 inches.

11. The fabric of claim 10 in which the space between adjoining portionsof adhesive in the spaced pattern is less than the average length of theindividual fibers.

12. A method for producing a laminated web from layers of highly-draftedfibers and plies of cellulose wadding; said method comprising the stepsof providing multiple slivers of staple length textile fibers containinga portion of thermoplastic fibers therein; juxtaposing said slivers inside-by-side relation and drawing the individual fibers in said sliversout to substantially their full length while parallelly disposed withother drawn fibers to form a tenuous web of highly-drafted andlongitudinally aligned individual fibers; positioning a continuous sheetof lightweight cellulose wadding sheet under said aligned fiber tenuousweb; moving said sheet and said tenuous web in the same direction atapproximately the same speed and depositing said tenuous web on saidsheet while providing oppositely reciprocating side-to-side motionbetween said tenuous web and said sheet at the point where said tenuousweb is deposited on said sheet whereby said tenuous web assumes aregular sinusoidal pattern of aligned fibers in contact with said sheet;and while maintaining said tenuous web and said sheet in contactapplying heat and pressure to said sheet to activate said thermoplasticfibers and "bond said tenuous web and said sheet into a unitary fabric.

13. The method of claim 12 in which fiber-faced surfaces of theresulting unitary fiber-wadding fabric are placed in face-to-facecontact with the sinusoidal pattern of fibers in one of said surfacesout of phase with the sinusoidal pattern of fibers in the opposingsurface, and hot calendering said contacting fabrics to reactivate saidthermoplastic fibers and bind said fabrics together.

14. A nonwoven fabric consisting essentially of at least one layer ofhighly-drafted individual staple length fibers extended to substantiallytheir full length and arranged in a sinusoidal pattern wherein theindividual fibers are substantially parallel to each other and at leastone layer of lightweight cellulose wadding; a portion of said fibersbeing thermoplastic; said thermoplastic fibers binding said fiber layerand said wadding layer together.

15. The fabric of claim 14 in which two of said fiber layers are inface-to-face contact with the sinusoidal pattern in one layer out ofphase with the sinusoidal pattern of the other layer, the fibers in onelayer intersecting and overlying the fibers in the other layer.

References Cited UNITED STATES PATENTS 11/1877 Turner et a1 156176X11/1960 Barnard 161l70X 11/1963 Bletzinger 16159X 4/1967 Romanin 156-4799/1946 Goldman 16157X 6/ 1964 Andrews 156289X 6/1967 Sokolowski 161143XWILLIAM J. VAN BALEN, Primary Examiner W. W. SCHWARZE, AssistantExaminer US. Cl. X.R.

